Additive manufacturing techniques have been known for decades and are currently used to produce a wide range of parts and articles suitable for any of a wide range of applications. The most common additive manufacturing processes may be grouped into three main categories: Powder bed sintering/melting, extrusion, and directed energy deposition by jetting/wire feed. One type of powder bed sintering/melting technique, which may be referred to as selective laser sintering/melting or direct metal laser sintering, utilizes a laser beam directed energy source to trace a design in a single layer of a powdered material. The heat from the laser sinters or melts the traced design into a solid piece with the thickness of that layer. A suitable material feed system may dispense another layer of powder on top of the layer just sintered. The process is then repeated until a three dimensional object is formed. However, the energy required to form each layer of material restricts the production speed and increases the cost of the equipment needed to produce an object, with ceramic materials typically requiring more energy than do metals, which in turn require more energy than do plastics.
Another process for forming articles is reaction synthesis. Reaction synthesis is a chemical process that can be used to form sintered materials much more rapidly than is possible with conventional sintering processes. A typical reaction synthesis process involves the mixing together of two or more reactants of dissimilar chemistry, typically in powder form. A die press may be used to compact the mixed powders, forming a compacted article or powder compact. Alternatively, a mold or crucible may be used to contain the powder mixture. Heat may then be applied to initiate a chemical reaction among the constituents. The process is often exothermic and results in the formation of one or more new phases. For example, the heat from a furnace or a flame can initiate a reaction in a mixture of titanium and carbon powder. The combination reaction releases heat and forms a sintered ceramic phase of titanium carbide. The heat produced by this reaction spreads to the powders around it, causing the reaction to propagate through any reactants present. Some such processes involve the addition of one or more inert species, often referred to as diluents, to control the reaction by absorbing heat.
Reaction synthesis techniques have been used to produce many types of materials including ceramics, metals, intermetallics, polymers, and composites. However, most reaction synthesis techniques require extensive processing steps including the design and fabrication of a die or mold and typically can only be used to produce articles of simple shapes with limited detail, thereby limiting such processes.